pH of Body Fluids
Start with the big picture
Arterial pH is normally 7.35–7.45; values below this range are termed acidemia, and values above it alkalemia. pH differs among body compartments: extracellular fluid is about 7.4, intracellular fluid about 7.0–7.2, and urine can vary from 4.5 to 8.0. Hydrogen ions arise from volatile acid production linked to CO₂ and from non-volatile acids, including sulfuric, phosphoric, lactic, and ketone acids. Buffer systems provide an immediate defense against pH shifts: bicarbonate is a major extracellular buffer, while phosphate and proteins contribute within cells and urine, and ammonia functions in renal tubules. The lungs regulate CO₂ relatively quickly; the kidneys adjust bicarbonate more slowly.
What you'll learn
- State the normal arterial pH range and distinguish acidemia from alkalemia.
- Compare approximate pH values in extracellular fluid, intracellular fluid, and urine.
- Identify volatile and non-volatile sources of hydrogen ions.
- Describe major buffer systems and their locations.
- Contrast the roles of the lungs and kidneys in pH regulation.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
